This invention relates to a process for the production of high molecular weight unsaturated hydrocarbon polymers having an increased proportion of vinyl groups or substituted vinyl groups, respectively.
Unsaturated hydrocarbon polymers, especially polybutadienes, are valuable basic materials, the low-molecular weight polymers being used primarily in the varnish and impregnating field, and the higher-molecular weight polymers being especially useful as rubbers. As is known, the properties of the polymers are greatly dependent on the steric configuration of the double bonds in the polymer. In detail, a differentiation is made among 1,4-cis-, 1,4-trans- and 1,2- or vinyl-double bonds.
Several processes have been known for the production of low-molecular polybutadienes with a high (&gt;95%) 1,4-content and molecular weights of 500 to 50,000 (German Pat. Nos. 1,186,631; 1,241,119; and 1,292,853). The products obtained according to these prior-art processes are, however, not suitable for all purposes, due to their high 1,4-content. There is a real need for products having an increased proportion of vinyl groups.
It is known from German published application DOS No. 1,720,998 to produce 1,2-polybutadiene having a high percentage of vinyl configuration, by polymerizing butadiene in a halogenated hydrocarbon as the solvent with a catalyst containing as the essential component organic phosphines of the general formula PR'R"R"', wherein R' and R" are alkyl groups and R'" is an alkyl or aryl group. However, this process is burdened with deficiencies. On the one hand, the halogenated hydrocarbons, which represent the only solvent usable in this method, are very toxic. On the other hand, the phosphines are very expensive and moreover make it impossible to produce high molecular weight polymers having vinyl contents in the range of interest in rubber technology, viz., between 10% and 70% 1,2-content.
German patent application No. P 23 61 782.5 describes a process for the production of low-molecular unsaturated hydrocarbon polymers having an increased proportion of vinyl and/or substituted vinyl groups, which in part eliminates some of the disadvantages of the relevant state of the art. That process is characterized by polymerizing conjugated dienes, optionally in the presence of a solvent, employing a catalyst system consisting essentially of (a) a cobalt compound, (b) a halogen-containing organoaluminum compound, (c) an organic phosphorus compound, and optionally (d) an H-acidic compound, wherein the catalyst component (c) is an organic phosphorus compound of the general formula ##EQU1## wherein R.sub.1, R.sub.2 and R.sub.3 can be an aryl or alkenyl group, or a general group OR.sub.4, OR.sub.5 or OR.sub.6, wherein R.sub.4, R.sub.5 and R.sub.6 signify an alkyl, alkenyl or monocyclic aryl. However, the low molecular polymers produced by this process cannot be utilized as rubbers.
It is an object of this invention to overcome the above-described disadvantages.